. Funding is requested to support travel for US participants to the Fifth International Workshop on Human Chromosome 21, to be held in Tsukuba, Japan. Originally, the conference was scheduled to take place June 15-17,1994, but it has been rescheduled for November 9 through 11 to meet the needs of the Japanese host. The overall goal of the workshop will be to continue the development of a detailed consensus map of chromosome 21. It is expected that a minimal tiling path of yeast artificial chromosomes (YACs) for at least the long (q) arm of the chromosome will be completed at this workshop. The use of new technologies for mapping, including restriction landmark genomic scanning (RLGS) and RecA assisted endonuclease (RARE) cleavage for facilitating the mapping of chromosome 21 will be assessed. The creation of a centromere and short (p) arm map of chromosome 21 has been undertaken, and evaluation of this endeavor will be essential to maximize the mapping of this significant fraction of the human genome. Progress in the utilization of new cloning systems, including P1 and bacterial artificial chromosome (PAC and BAC) systems will be assessed, as will the format of future chromosome 21 workshops.